In recent years, attention has been focused on a vehicle that uses an electric motor as a drive power source, such as an electric vehicle, a hybrid vehicle, or a fuel-cell vehicle, from an environmental standpoint. Such a vehicle is mounted with a power storage mechanism made of a secondary battery or an electric double layer capacitor, for supplying electric power to the electric motor and for converting kinetic energy into electric energy and storing the same during regenerative braking.
In such a vehicle that uses an electric motor as a drive power source, it is desirable to increase a charge/discharge capacity of the power storage mechanism so as to improve traveling performance such as acceleration performance or continuous traveling distance.
On the other hand, the power storage mechanism utilizes an electrochemical action to store electric energy, so that its charge/discharge properties tend to be influenced by temperatures. In a typical power storage mechanism, its charge/discharge performance is deteriorated as the temperature decreases. Therefore, temperature management, particularly temperature-raising control, of the power storage mechanism is important to maintain prescribed charge/discharge performance.
For example, Japanese Patent Laying-Open No. 06-24238 discloses a battery temperature control device that controls a temperature of the battery mounted on an electric vehicle to fall within an appropriate temperature range. According to the document, the battery temperature control device includes a circulating water channel for cooling/heating the battery. The circulating water channel is provided to allow cooling water inside a thermal insulating vessel for the battery to circulate to a radiator that exchanges heat with air outside the vehicle or to a heat core that exchanges heat with air inside the vehicle, and also allow the cooling water to circulate to an inverter and a motor both identified as a heat-generating member that generates heat by the startup of the vehicle. When the temperature of the battery is lower than an appropriate temperature during charging in winter or the like, when the temperature of the battery is lower than an appropriate temperature at startup, or when the ignition is turned on and the vehicle speed is zero, the battery temperature control device heats the battery by means of an electric heater provided at the thermal insulating vessel for the battery. In contrast, if the vehicle speed is not zero (i.e. during traveling) and the motor and the inverter are at a temperature at or above an appropriate temperature, the battery temperature control device heats the battery by utilizing heat released by the motor and the inverter.
Further, Japanese Patent Laying-Open No. 06-231807 discloses a battery-warming device for an electric vehicle, having batteries disposed around a fuel-fired heater for warming a vehicle chamber, and having transmitting means for transmitting exhaust heat of the fuel-fired heater being in an operating state to the battery.
As to the battery temperature control device disclosed in Japanese Patent Laying-Open No. 06-24238, there is disclosed a configuration that utilizes heat released by the motor and the inverter to heat the battery. However, if the motor and the inverter are at a temperature lower than an appropriate temperature, such as at the startup or at a vehicle speed of zero, there is adopted a configuration in which the electric heater is turned on to heat the battery.
Therefore, in Japanese Patent Laying-Open No. 06-24238, it is necessary to provide the electric heater and a power supply for the electric heater at the thermal insulating vessel for the battery, and hence there arises a problem of increase in size and cost of the battery temperature control device.
Further, as to the battery-warming device disclosed in Japanese Patent Laying-Open No. 06-231807, there is disclosed a configuration in which the fuel-fired heater is disposed at the center of a battery tray, and a plurality of batteries are disposed around the fuel-fired heater. Therefore, it is difficult to achieve reduction in size and cost of the battery.
The present invention has been made to solve these problems. An object of the present invention is to provide a cooling system capable of raising a temperature of a power storage mechanism by a small-sized, low-cost device configuration.